RFC 1171 (rfc1171) - Page 2 of 48
Point-to-Point Protocol for the transmission of multi-protocol datagrams over Point-to-Point links
Alternative Format: Original Text Document
RFC 1171 Point-to-Point Protocol July 1990 asynchronous or synchronous duplex circuits, either dedicated or circuit switched. 2. An extensible Link Control Protocol (LCP) to establish, configure, and test the data-link connection. 3. A family of Network Control Protocols (NCP) for establishing and configuring different network-layer protocols. PPP is designed to allow the simultaneous use of multiple network- layer protocols. In order to establish communications over a point-to-point link, the originating PPP would first send LCP packets to configure and test the data link. After the link has been establish and optional facilities have been negotiated as needed by the LCP, the originating PPP would send NCP packets to choose and configure one or more network-layer protocols. Once each of the chosen network-layer protocols has been configured, datagrams from each network-layer protocol can be sent over the link. The link will remain configured for communications until explicit LCP or NCP packets close the link down, or until some external event occurs (e.g., inactivity timer expires or user intervention). 1.3. Organization of the document This memo is divided into several sections. Section 2 discusses the physical-layer requirements of PPP. Section 3 describes the Data Link Layer including the PPP frame format and data link encapsulation scheme. Section 4 specifies the LCP including the connection establishment and option negotiation procedures. Section 5 specifies the IP Control Protocol (IPCP), which is the NCP for the Internet Protocol, and describes the encapsulation of IP datagrams within PPP packets. Appendix A summarizes important features of asynchronous HDLC, and Appendix B describes an efficient table-lookup algorithm for fast Frame Check Sequence (FCS) computation. Perkins
